This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-229969 filed on Jul. 30, 2001.
1. Field of the Invention
The present invention relates to a method for joining a coil wire, which has a heat resistant coating, to a coil terminal.
2. Description of Related Art
Various techniques, such as fusing or soldering, has been used for joining a coil wire and a coil terminal to each other. In the case of fusing, the wire and the terminal need to be directly clamped and energized by corresponding electrodes. Thus, a space for accommodating the electrodes is required.
In the case of soldering, soldering flux needs to be applied to the coil wire and the coil terminal before soldering them together. Furthermore, when eutectic solder is used to solder the coil wire and the coil terminal together, a lead content in the eutectic solder gives rise to environmental concerns due to its toxicity. Also, if the coil wire is a heat resistant wire having a heat resistant dielectric coating around it, the soldering cannot be performed directly on the heat resistant wire through the coating. Thus, the heat resistant coating needs to be removed from the coil wire by a mechanical or chemical process before the coil wire is soldered to the coil terminal.
Each of Japanese Unexamined Patent Publication No. 2000-190068 and Japanese Unexamined Patent Publication No. 2001-87854 discloses a method for joining such a heat resistant wire and a coil terminal to each other.
In the method disclosed in Japanese Unexamined Patent Publication No. 2000-190068, a joint portion between the coil wire and the terminal is first covered with a joining aid material, and arc welding is performed on it to join them together. However, this method additionally requires the joining aid material and a process of covering the joint portion between the coil wire and the terminal with the joining aid material.
In the method disclosed in Japanese Unexamined Patent Publication No. 2001-87854, high-purity oxygen is supplied to the joint portion, and the heat resistant coating of the coil wire is combusted or burnt. However, when the high-purity oxygen is used, it is difficult to control a burning rate of the heat resistant coating, so that the coil wire and the terminal can possibly be burnt together with the heat resistant coating. Furthermore, when the high-purity oxygen is used, it must be handled with care. Also, the use of the high-purity oxygen disadvantageously increases manufacturing costs.
The present invention addresses the above disadvantages. Thus, it is an objective of the present invention to provide a method for joining a coil wire, which has a heat resistant coating, and a coil terminal to each other in a simple and effective manner that allows effective removal of the heat resistant coating from a joint portion between the coil wire and the coil terminal.
To achieve the objective of the present invention, there is provided a method for joining an end portion of a coil wire, which has a heat resistant coating, and a coil terminal to each other. In the method, the end portion of the coil wire is wound around the coil terminal to form a wound portion. Then, air is supplied to the wound portion. Next, heat is supplied in a first stage to the coil terminal, and thus the heat resistant coating is removed from at least a portion of the coil wire located in the wound portion. Thereafter, heat is supplied in a second stage to the coil terminal, and thus a portion of the coil terminal is melted to join the coil wire and the coil terminal to each other at the wound portion.